Jim - great combacks.
I ask if the racist has ever had a blood transfuson, then let him/her know that I have it on good authority that the race in question in his area is known to sell the largest percentage of blood collected.
The other that works for me is simply be whatever it is they can't stand. It's fun arguing a point of view that you yourself can't tolerate. Sometimes my wife wishes I wouldn't profess to being gay with her sitting beside me. That backfired once. Seems the husband of a couple in our midst in the Virgin Islands was a closet gay. He didn't appreciate the humor when I set him straight, pardon the pun.
For hellions, simply say that "my kids behave a lot better than yours". They response I usually get is that normally their's behave but they are on vacation so all rules are off. They should have fun.
When I lived in the Caribbean, the response to my objections to cutting in line was, "they are in a hurry. If you are standing in the line, you obviously aren't in a hurry". Have to be quick to parry that one. Same as when they picked the lemons off our tree. "If you wanted them, you would have already picked them". Have to admit it makes sense.
A disgusted "don't you ever talk about anything else" sometimes will get them off bodily functions. When one returned to the table after announcing exactly why he had to leave, I told him that since his eyes were blue, it must have been successful. Usually the wife gets it while it all goes over the head of the offendee.
That's the advantage to a table for six or eight. The others usually back you up and greatfully join in your converstation, excluding the boor.